When machining parts and components, either the parts to be machined and/or the tools for machining are connected to adjustment devices or to the machines by means of palletizing devices. These palletizing devices comprise each at least one pallet and at least one pallet counter-plate or pallet receiver to be interconnected onto which either the part to be machined or the corresponding tool is fastened. The advantage of palletizing consists in that the, thus, palletized objects can be placed and secured, particularly automatically, in a well-defined position onto several machines for adjustment, machining or measuring with a minimum expenditure. Therefore, a number of different palletizing apparatus are known according to the prior art.
In principle, each palletizing apparatus comprises some units consisting of two coupling elements to be interconnected and a connection arrangement for clamping these coupling elements in the direction of a predetermined clamping axis which passes centrally through the elements. Apart from any releasable interconnection of the coupling elements, a palletizing system should enable a defined orientation with respect to coordinates at least in one direction. The clamping axis is generally considered to be the z-axis whose zero point is defined by z-contact surfaces. In order to ensure a well-defined orientation of the respective x-axis or y-axis which are perpendicular to the z-axis, there is at least one orienting arrangement.
From DE-A-41 35 418, a connection device is known which achieves clamping of the coupling elements through a bolt and recess arrangement wherein springs press balls of a ball cage into a groove of the bolt. For releasing the connection, the clamping force of the springs is overcome by a hydraulic plunger.
There are other systems which comprise several coupling elements, particularly four, on each the pallet and the pallet receiver, the coupling elements ensuring clamping of the zcontact surfaces, but allowing some tolerance in x- and y-direction. In order to ensure a well-defined x- and y-orientation, a pair of orientation elements for each orientation axis are fixed to the pallet and the pallet receiver, the elements of one of the latter parts, i.e. the elements of the pallet, but optionally those of the pallet receiver, are resilient, while the respective complementary one, i.e. that of the pallet receiver or that of the pallet, is rigid. These orientation elements for the x- and y-orientation, when interconnected, allow some expansion or shrinking displacement along the respective axis, the point of intersection of the x- and the y-axis, however, remaining stationary, thus forming a zero point, while any turning movement about the z-axis is prevented by engagement transversely to the respective orientation of two of each interconnected pairs of orientation elements in x- and y-direction. Such a palletizing device is based on a standard pallet size defined by the arrangement of the orientation elements. Each pallet has to extend at least over the region of the orientation elements. This means that another set of orientation elements have to be provided for smaller pallets. Although, with pallets extending over the double length of a standard pallet, two x-y-orientation systems could by arranged side-by-side, but this would cause problems due to redundancy and two interconnected zero points when the pallet and the pallet receiver elongate differently. Moreover, manufacture of such pallets and pallet receivers is very expensive, because the orientation elements have to be arranged individually in a highly precise manner. In addition, this known palletizing device is not adaptable to individual needs.
Constructive solutions are also known in which x-y-orientation is effected by the coupling elements. One unit is provided with two interconnectable coupling elements fitting very precisely and defines a common zero point. The units along an x-axis and an y-axis leading through this zero point have some tolerance in the direction of the x- or y-axis, but are substantially free from any play transversely to the x- or y-axis. Units which are neither situated on the x-axis nor on the y-axis have to have some play in all directions. If a pallet receiver and a corresponding pallet is to be built up with four units or four coupling elements each, three different types of units have to be used, i.e. in the zero point a matching zero point unit, along the axes units which have some tolerance in the axis' direction, and beside the axes units having some play or tolerance in all direction of the x-y-plane. With such units, it is possible to build up palletizing devices of various size, but the use of three different types of units is awkward and favors mistakes.
A coupling device or unit is known from EP 0 111 092 B1 which ensures centricity corresponding to the use of conical seats as well as a well-defined angular position relative to interconnected members or coupling elements in a plane perpendicular to the central axis. Centricity and impossibility of any displacement transversely to the central axis is ensured by a conical trunnion which is pressed into a fitting, precisely circular opening of a disk fastened to one of the members. The marginal edge is somewhat deformed central symmetrically upon clamping. Deformation transversely to the axis is prevented by inherent stability of the circular opening and the disk area surrounding the opening completely. To maintain the angular position precisely, an eccentrically arranged oval opening having radius parallel margins is formed in the disk, while another conical trunnion is provided on the other member so as to be pressed into the oval opening. In order not to affect centering by the second trunnion, a slot is formed within the disk which extends between the two openings. Exact positioning on different machines is only possible, if both trunnions and the two openings are machined very exactly and the disk is mounted with high accuracy. Both members are interconnected by a centrally arranged clamping screw. By this approach, the zero point is not maintained by two intersecting fixed axes, as mentioned above, but by a point-wise fixation. In addition, the axis extending through the point fixation is fix. Thus, the use of a plurality of such coupling devices on a palletizing device is not possible or not suitable due to redundancy problems.
EP-B-0 267 352 discloses another approach in which highly precise coupling of two parts is achieved even if one of the interengaging parts is formed resiliently with some tolerance. One of the parts comprises pillow block-like elements arranged in a circle around the zero point and having grooves which point radially away from the zero point. The grooves are resilient so that precisely arranged profiles of the other part can deform the grooves slightly in peripheral direction when the profiles are inserted into the grooves. In order to ensure precise positioning with respect to the x- and y-axes even with some tolerances in manufacture, at least three grooves and, correspondingly, three profiles have to be provided in equal angular distances around the zero point. The elasticity of the grooves is only provided in order to make the parts interconnectable even with small inaccuracies of one of the parts. The elasticity should be, however, not so that the zero point is not sufficiently precisely defined. Since the zero point and the angular orientation are fixed very precisely with one unit of two interconnectable parts only, the use of a plurality of such coupling devices on an individual palletizing apparatus is not suitable due to redundancy problems. In addition, machining the highly precise part having a prolongation in z-direction and of profiles extending radially from the latter in precisely defined directions is very expensive. The pillow block-like elements having elastic properties transversely to the radially extending groove involves high expenditure in manufacture and assembly.